fix: eliminate PR contamination from broad git staging (#777)

[diberry]

Summary

Eliminates all broad \git add\ patterns that cause PR file contamination when multiple agents work concurrently.

Changes

Fix	File	What changed
1	.squad-templates/issue-lifecycle.md\	Replace \git add .\ with explicit file staging
2	.squad-templates/scribe-charter.md\	Scope \git add .squad/\ to specific Scribe files
2	.squad-templates/squad.agent.md\	Same scoping in Scribe spawn template
3	.copilot/skills/git-workflow/SKILL.md\	Replace \git add -A\ with explicit staging
4	.copilot/skills/windows-compatibility/SKILL.md\	Replace \git add .squad/\ with explicit paths
5	\scripts/sync-templates.mjs\	Gate behind --sync\ flag or \SQUAD_SYNC_TEMPLATES=1\ env var
bonus	.github/agents/squad.agent.md\	Fix live agent copy (same as Fix 2)

Pattern

All broad staging commands (\git add ., \git add -A, \git add .squad/) replaced with explicit file lists targeting only files the agent actually modified.

Closes #777

[github-actions]

🛫 PR Readiness Check

⚠️ 2 item(s) to address before review

Status	Check	Details
✅	Single commit	1 commit — clean history
✅	Not in draft	Ready for review
✅	Branch up to date	Up to date with dev
❌	Copilot review	No Copilot review yet — it may still be processing
✅	Changeset present	No source files changed — changeset not required
✅	Scope clean	No .squad/ or docs/proposals/ files
✅	No merge conflicts	No merge conflicts
✅	Copilot threads resolved	All 6 Copilot thread(s) resolved
❌	CI passing	5 check(s) still running

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[Copilot]

Pull request overview

This PR aims to eliminate pull request “contamination” by removing broad git add patterns from Squad templates/skills and by preventing unintended template mirroring from running implicitly.

Changes:

• Replaces broad staging commands (git add ., git add -A, git add .squad/) with more targeted staging guidance in templates and Copilot skills.
• Updates Scribe-related templates to discourage staging the entire .squad/ directory.
• Adds an “explicit invocation” guard to scripts/sync-templates.mjs (requires --sync or SQUAD_SYNC_TEMPLATES=1).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
scripts/sync-templates.mjs	Adds a guard intended to prevent accidental template sync runs.
.squad-templates/issue-lifecycle.md	Replaces git add . guidance with explicit-file staging guidance.
.squad-templates/scribe-charter.md	Replaces git add .squad/ with a narrower (but still glob-based) staging command.
.squad-templates/squad.agent.md	Updates the Scribe commit step to avoid git add .squad/ (still uses glob examples).
.github/agents/squad.agent.md	Mirrors the same Scribe commit-step guidance for the live agent file.
.copilot/skills/git-workflow/SKILL.md	Replaces git add -A with explicit-file staging guidance.
.copilot/skills/windows-compatibility/SKILL.md	Introduces a new skill doc with Windows-safe patterns and updated staging guidance.

[tamirdresher]

LGTM. Critical fix for agent coordination — replaces all broad git add with explicit staging across 18 files. Good Windows compat guidance.